CD90-positive stromal cells associate with inflammatory and fibrotic changes in modic changes.

Area of Science:

• Spinal pathology
• Bone marrow imaging
• Histopathology

Background:

• Modic changes (MC) are vertebral bone marrow lesions linked to disc degeneration and low back pain (LBP).
• Previous studies qualitatively described MC histopathology, with limited patient samples.
• CD90-positive bone marrow stromal cells have been implicated as pro-fibrotic in MC.

Purpose of the Study:

• To conduct the first semi-quantitative histomorphometric analysis of bone marrow in Modic changes.
• To investigate the potential role of CD90-positive cells in the pathomechanisms of Modic changes.

Main Methods:

• Human vertebral bone marrow biopsies from Modic type 1 (MC1), Modic type 2 (MC2), and control (MC0) groups were analyzed.
• Histology and immunohistochemistry were used to score inflammatory and fibrotic changes, and bone marrow stromal cell populations (CD90, CD105).
• Statistical analyses including non-parametric tests, correlations, clustering, and principal component analysis were performed.

Main Results:

• MC1 and MC2 showed significantly higher scores for CD90-positive cells compared to controls (MC0).
• MC1 exhibited increased connective tissue, edema, and inflammatory infiltrates compared to MC0.
• CD90 scores strongly correlated with inflammatory and fibrotic markers, and connective tissue amount correlated with LBP severity.

Conclusions:

• CD90-positive cell accumulation is a key feature of Modic changes in patients undergoing spinal fusion.
• These cells are associated with inflammatory and fibrotic changes within the bone marrow.
• CD90-positive cells likely play a significant role in the inflammatory-fibrotic processes underlying Modic changes and LBP.